Light projector



R. WENDEL LIGHT PROJECTOR Sept.. 6, 1949.

2 Sheets-Sheet 2 Original Filed Jan. ll, 1941 lNVENTO R /Puq/o/f Wende/ ATTORNEYS atenfed ep. 6,1949

'UNITED S TAT ES .JPA'T G 'C LGHT PROICTOR Rudolf Wendel, Roslyg'i Heighta-N. ;Yi

Orginaljappli'cation January 1'1, 1941, m'Serial-No.

The present inventionn'elates .to .light projectars, and more partioularly to projeotors wherein Ithe projected beam 'or vb'ea'rns 'are caused to travel along Jselected for predetermined paths.

This-application is .a division of my application It is one of'the objects of the invention to provida a projector which is capable of directing-the lrays of light either vin a parallel beam or along a beam of any desired a'ngular spread Without ;the

aid of .glass .lenses or the like, thereby to produoe gr van extremely simple and vinexpensive construc- More particularly, .it is an object of the invenfitio'n 'to provide a projector Whichmayfbedesoribed `as being of the liquid lens or, more specifically, water lens type, Whichis designedfor immersion .lin a body of liquid, usually water, or tobe Vsur- `zrounded by a, preferably circulating, body of liquid, and Whose outer casing or bulb is shaped in dependence on the indices of refraction of its Vown material and of :the surrounding liquid .and in such manner that either a parallel-ray beam or a beam whose 'raysdverge at a predetermined -angle is obtained.

.It is a further object of the invention to con- .1. .struct a projector in such manner that selected lregions about the same are uniformly illuminated thereby while the source of light is completely `concealed.

Other objects of the invention will` appear from the following detailed description of the inven- `tion.

Projectors constructed in 'aocordance 4With i the `inv'ention are-suitable for use in practically -all situations whereuniform illumination, or illumination'of limitedareas or in certain'directionsis desired. Thus my ,improved projeetor may be used in swimming pools and in fountainsbeneath the surface of the water, or in .lighthouse Vpro- .:J'eotors, road illuminators, etc., being in thelatter two and similar cases provided JWithya transpar- .ent jacketfcontaining Water vor other liquid for .provicling' the water lens,anddesirably-also for coolng thelamp. Inzeach casethe water or other liquid into .which the light is directedacts aspart v of `the lens, the other part bki-ngthe `suitably shaped outer 4casing or ;bulb of the -lamp proper. Where it is4 desiredto oorioeal the source` of light, as in :the .illnminatin .of .zSw-immine-poql, foun- -taina roadwaY-;Sz ;air fields, and the like this .may beaccomnlishd byshieldine ,parts .Of the lamp in combination Withfsuitablepositioning thereof, as

The liquid lens ,provided by the present invention may be .considered to zbe:2f..p1ar1.0-0nvex haracter. .the .envexfsurfae of the lens. being determinedby zthezshan Q'fthe transparent V(inter oasingor bulb oftheprojecton The shape of such casing orbulbjisdeterininel aceordance With well-known optical pri-nciples to cause the rays reectedoneateriile the bodzyfi 'liquid '20 travel VVinp,recletermine,d direotions. The outer oasing or bulb ispreferablymagle-;in the form of a body of revolution and thebod of liquid,fi genera1ly water,

.contaeting the outevrzsurfiaoe of the asing or bulb,

forms in effect ;an annu-lar lens. When the proectorfis zemployed as abeacon, or for illuminating a fountain or .the like, the Llens ,will be effective through an angle'of; ;for use `-in a 'swimining pool, the Vang-le oflthe'beamwill be about 18, or

`slightly more,asfexp1ained.below. -*he direction of the refiectedrays will be determined primarily by `the index jofrefraction'of 'the liquid With;ref-

erenoe to the mediumiinside the casing ;or bulb,

the Vn'iaterial of the casing or bulb itself being Without effect upon such direetion as Athe wall is made of as uniformthicknessaspossible.

The inventin is illustrated by Way of example on the aecompanyingdrawings, wherein Figi -1 illustrates a projectorconstruction,in accordance With .the `invention adapted to be positioned below the surfaeeofthevvater in the Well of a fountain .forf-,illuminating both the body of Water in the VWell and'the spray above the Well;

Fig. 2 .showsraform of'construct'ion suitable for lififhthouse lamps, and-for the illumination of roadways, air.fields, andthe like. A

The projector-shownlin Fig. 1 zis constructed 'toV effect illumination both -of the spray of a fountain as well as of the ;body`` of water in the Well of the fountaim ;fI-*o this-endfthe glass casing 2 io is'so shaped-astoprovide.both a convexannular water lensabout itscentral portion and a convex Water lens fat the 4top thereof to direct thebeams along predeteriined directions,. whi1e at the same time preventing the escape of ,light in directions meeting the. eyes of. observer's about ;the foun`tain,so thatthesourceof .light riains .concealed .'fheflprojectoriis preferably, although `vnot necessarilyflockated directly below thei'lo'zzle 'll of the fountain and is supported directly from the bottom of the fountain by way of a bracket which is secured to the fountain floor by screws 19 or the like. The braoket 18 is composed of a solid metal plate and serves as the bottom or closure for the lower, open end of the casing 2 lc. The bracket includes an annular flange 80 which is sealed against the bottom portion of the casing Zlc with the aid of a sealing ring 23 of rubber or the like, the ring being pressed between the flange 80 and the casing by means of a clamping ring 8| which is secured to the flange by way of screws 82. The bracket 18 has a raised central portion 83 upon which the socket 26 of the bulb 21 is supported. The conductors are led from the socket by way of a metallic or other Water-proof pipe 21a, the latter being led off through a threaded side extension 84 of the bracket, the end of the extension being sealed against the pipe by way of a sealing member 8'5 and union 86. The interior of the casing is thus protected against the entry of water.

To prevent light from reaching the eyes of spectators at the edge of the fountain, or at a distance therefrom, the outer edge portion at the top of the casing 2 |c is coated with a black paint, as shown at 81, or provided with any other suitable opaque covering; while a similar coating or covering 88 is provided at the bottom of the casing. The emerging rays of light L thus travel only in predetermined directions, the side rays being directed more or less horizontally into the body of water in the well of the fountain, while the upwardly travelling rays are directed more or less vertically against the spray of water W discharged by the nozzle 11. The lighting effect is one of great beauty as the drops of lwater in the spray take on the character of illuminated diamonds, while the body of water at the bottom of the fountain gleams with an internal luminesoence whose source is not visible.

In the case of a fountain, the rays may diverge, depending on the size of the well, as much as about 30 in the Vertical plane (i. e. about 15 to the horizontal) without rendering the source of light visible from above the surface of the water in the well. This is due to the fact that within an angle of about 15 to the horizontal, the light is reflected from the surface of the water back into the well, and where it is desired to illuminate also the floor of the well, the casing 2lc will be constructed in such a manner as to cause the rays to diverge up to as much as 15 to the horizontal. The floor will then be illuminated both by rays reaching the same directly from the lamp and by rays refiected directly from the surface of the water.

In the construction of the outer casing 2|c there are taken into account the direction from which the light strikes the inner wall of the casing, and the indices of refraction of the material of the casing and of the water. The effective portion of the casing is given a shape such that rays passing therefrom into the water will have a maximum angle of divergence of above 15 to the horizontal. With this limiting angle in view, and the indices of refraction of the material of the casing material and of the water being known, the shape of the casing can be readily determined by those familiar with the laws of optics.

The casing forms with the water adjoining the same a combination lens which in the form of the invention illustrated in the drawing can be considered as of plano-convex shape, the convex surface being provided by the Outline of the lamp casing, and the plane surface by the body of water. It will be understood that the casing will be made of a material which can withstand the temperature differences to which it must be subjected in use. The lamp is eifectively cooled by the water surrounding the same.

As will be clear from the above description, the projector will emit a beam through a predetermined horizontal angle, the rays being either parallel or having a limited degree of divergence. The light emitted by the projector is uniformly distributed through the body of water and then combined with the refiection of the light from the disturbed surface of the water into the body of water produces a shimmering and fluorescent effect which is very beautiful and gives the appearance of a uniformly illuminated and glowing mass of water. The total concealment of the source of the light further adds to the mysterious and magical efiect.

- The lamp can be readily constructed for mounting as a unit within the well, and broken parts can be easily and inexpensively replaced. All of the non-transparent parts immersed in the water may be made of or coated with a material, such as copper, bronze or the like, which is capable of withstanding the corrosive action of the water.

As shown in Fig. 1, the Outline of the curved walls of the casing will be of generally parabolic shape in cross-section. The specific Outline, as already explained, will depend upon the direction of the rays striking the casing from the interior, and upon the indices of refraction of the glass or other transparent material of which the casing is made, and of the water. The refractive index for glass may be taken as 1.5 while that of the water is 1.3 with reference to a value of 1 for air. The height of the annular water lens about the curved region can be Varied within limits determined by the minimum safe distance between the casing and filament and by considerations of size. A height of lens which subtends an angle of about 71 at the filament has been found to be satisfactory.

The projector may, of course, be designed for a spread of 360, as where the projector is to be used as a beacon, but usually a spread of less than 360 will be required.

Fig. 1 shows a construction in which the lamp filament is arranged along the central line of the projected beam; but it will be obvious that this relationship is not essential and that the shape of the casing can be altered to obtain any desired direction of beam. Also, the filament can be located elsewhere than at the approximate center of the casing, in which case the shape of the casing may assume a less regular or symmetrical form than in Fig. 1, for obtaining special lighting effects.

While the critical angle" for water with respect to air, that is, the angle at which total refiection back into the water occurs, is about 41 to the horizontal, I prefer to limit the angle to the horizontal of the projected rays to about 15-20, in order to avoid reducing too greatly the intensity of the beam in the region of the walls of the well, and also to avoid producing a brightly illuminated area on the bottom of the well close to the lamp.

For use in lighthouses and for the illumination of roadways, airports and the like, that is, in situations wherein the projector is not employed to illuminate a body of water. the construction shown in v;2 presents a .simpleand ;inexpensive projector for obtaining a highly efficient i l1u1 ni.- nation. VIn this form of the invention the puter :casing may at the same time constitutethe :lamp bono, as already indicatea, or n ;may be .designed to receive a .separate "lamp bulb as shownjin Fi'g. `1. The sides of the 'casing '2,111' :are shapd-jn the manner described 'hereina'boya angl`l accordance with the inventionithecasingtisin'- rounded 'by ,a jacket 89 which'is designd'llo receive a body of cooling'water which at 'the same time acts as azlensfagai'nstthenuryed and roughly parabolic outline of the oaing- The casing may .be securecll in water-tight relation to ahood IB in the manner described v:here'inabove, thelzloyver dampmg ring v Servine .a nie same. am- ;e as

a ,Suspension for'the iacket 89 which, as,. shp.wn,

is made of glass or other transparent material. A sealing ring or gasket 90 seals the jacket against the ring 20h with the aid of a clamping ring 9|. The water in the jacket circulates thermo-siphonically through a cooling coil 92 located externally of the jacket and connected in water-tight manner with the upper and lower portions of the jaoket 89. It will be understood that the water in the jacket becomes heated during the operation of the projector and flows upwardly into the coil 92, and after being cooled in the latter, returns to the bottom of the jacket. The projector shown in Fig. 2 is designed especially for use in lghthouses and the outline of the sides of the casing 2 I d is so determined that the rays emerge in a more or less parallel beam from the projector. The beam may extend horizontally through approximately 360, or for such fraction thereof as may be desired; in the latter case, suitable shields are provided, and, if desired, a refiector of the type shown at 36 in Fig. 1 of my above-mentioned patent may be located in the jacket 89 outside of the casing 2|d, or inside of the latter when a separate light bulb is employed. The source of light may, of course, be either an incandescent filament, an electric arc, a fluorescent lamp, or the like.

It will be seen from the foregoing that I have provided a projector which is capable of directing the light rays along predetermined paths without the aid of any special lenses, or special cutting or grinding, the casing of the projeotor being of more or less uniform thickness throughout and being readily manufactured at a low cost. The distribution of light is both efiicient and uniform, and as indicated above, highly ornamental effects can be obtained therewith when employed for illuminating either more or less stagnant or moving bodies of liquid.

In general, for use in lighthouses and for the illumination of airflelds, roadways, and the like, an exactly or very nearly horizontal beam, i. e. one in which the rays are parallel or practically so, will be preferable, as thereby a more concentrated beam will be obtained, and the outline of the casing or bulb Will be shaped accordingly to produce the requisite Water lens effect.

In both of the -constructions of Figs. 1 and 2, it will be observed, at least part of the respective casings are designed and positioned so as to direct a beam of more or less predetermined shape and direction into the atmosphere above or surrounding a body of liquid such as water forming a water lens with the respective shaped portion of the casing. In this respect the structure and function of the projectors descrlbed herein difier from the illuminating device for swimming pools .and thelzike deseribedand snecificallyvclaimfl in my above-mnfioned Vpatent application.

The water supply ;line to the snravnozzle in ;Eis- 1 :is advantageousl'y inclinedto the horizontal to avoid producing .ashadowona 'while in the constructionV .of Rig- ;2 the thermo-.sinhonic tir.- culation can, ofcourse, he replaced .by forced .circulation by means .of .a pump, especially :the case .of large, hiehrpoweredunits- Theoasine or bulb which -fortnsthe water lens is best constructed as a body. of revolution, although this is mt essential 'where the horizontal spread of the emitted beam is less thanid These parts are preferably made of well-annealed glass, although other transparent material, oolored or not, may be used.

It will be `understood that, as described more fully 'in my aforementioned patent, the sides ,of the casing in Fig. 1 are so shaped' that the rays passing into the surrounding body of water in the well have a maximum angularity with reference to the horizontal plane that substantially no laterally directed light rays from the projector emerge from the surface of the well, so that no rays reach the eyes of spectators about the fountain, and the source of the illumination thereby remains concealed.

I claim:

1. The combination with a fountain structure comprisng a well and means for forming a Waterspray above the surface of the well, of a projector for illuminating the spray and the collected water in the well, comprising a transparent casing adapted to be supported in the wall of the fountain below the surface of the water, and a source of light within the casing, the sides of the casing being so curved as to shape the body of water about the same into the form of an arcuate lens which directs the rays into the body of water in asubstantially horizontal direction, the upper portion of the casing being likewise curved to direct the rays upwardly into the spray and out of the line of sight of spectators about the fountain, whereby the source of illumination remains concealed.

2. A projector as set forth in claim 1, including shades at the upper and lower edges of the casing for preventing the emission of uncontrolled rays either into the atmosphere or against surfaces in the vicinity of the projector.

3. The combination with a fountain structure comprising a well and means for forming a waterspray above the surface of the well, said fountain having a nozzle above the well for producing the spray, of apparatus for illuminating the water in the well and in the spray of the fountain while concealing the source of light, comprising a projector located in the well beneath the nozzle, means for supporting the projector within the well and below the surface of the water therein, said projector including a transparent outer caslng open at its bottom end, a socket for a lamp bulb within the casing, means for securing the open end of the casing to the support in watertight manner, the side portions of the casing being of curved Outline to form with the surrounding body of water an arcuate water lens of such configuration that light rays emanating from the bulb are directed through a horizontal arc into the water in an approximately parallel horizontal beam, whereby substantially no light rays from the projector emerge from the surface of the pool, and the top of the casing being likewise shaped to produce a water lens effect with the contiguous body of water to direct light from the 7 bulb along a beam of predetermined'fo'ni galinst the water spray from the' nozzle. 1

4. Apparatus as set forth in claim 3 including 'shields arranged to prevent the emergence of REFERENCES CITED The following references are of record in the file of this patent:

Number Number 58 lUNITED STATES PATENTS w Name' Date Berger et al. Dec. 22, 1891 Eldridge Sept. 27, 1892 Hollnagel June 25, 1929 vBoe'rstler Jan. 27, 1931 Rothen Feb. 10, 1931 Profiatt Jan. 5, 1932 Lorenz Jan. 31, 1933 Wheat Sept. 11,'1934 FOREIGN PATENTS i Country Date Germany Feb. 5, 1926 Germany 1980 France 1929 France Feb. 24, 1936 

